Automatic load holder for testing machines



Feb. 20, 1940. I R, gw s 4 2,191,282

AUTOMATIC LOAD HOLDER FOR TESTING MACHINES Filed March 26,1937 3 Sheets-Shea} IINVENTOR I fiuWfiM ATTORNEY Feb. 20, 1940. R. B. LEWIS 1,

AUTOMATIC LOAD HOLDER FOR TESTING MACHINES Filed March 26, 1937 3 Sheets-Sheet 2 INVENTOR BY t ATTORNEY Feb. 20, 1940. R. B. LEWIS 2,191,282

AUTOMATIC LOAD HOLDER FOR TESTING MACHINES Filed llarch 26, 1937 3 Shets-Sheet s u t \9 Q} N INVEN QR I a m ATTORNEY Patented Feb. 1940 [t eeter- E vania plication March 26, 1937, Serial No. 133,190 12 Claims (01.. 265-19 The object of jthis invention is to devise a novel automatic 'loadholder for hydraulic test ing machines which will hold the load regardless of changes in viscosity of the hydraulic medium; This means that a, predetermined pressure is kept on the specimen in the testing machine regardless of changes in viscosity of the oil or hydraulic fluid. A valve in the'feed linefrom a m: pump to the pressurecylinder of the testing ma chine determines the speed of cross head action of the testing machine and is proportional to'the valve opening, As the oil heats up due to the pressure created, the viscosityis affected, and leakage around the ram in the pressure cylinder f increases to reduce thepressurein'the pressure cylinder below the required predetermined pressure.

It will thus be clear that unless some means is provided to increase the pressure in the pressure cylinder, the predetermined pressure or'load will not be maintained test.

Other novel vantage will hereinafter more clearly appear in E the detailed description and the a'ppende'd claims. For the purpose of illustrating theinvention, I have shown in the accompanying-drawings typical embodiments of it, which, in practice, will give features of construction and adreliable and satisfactory results. It is, however, to

35 ization of these instrumentalities as herein set forth v I Figure lis afront elevation of a'hydra'ulic type testing machine in conjunction with which the present'invention maybe employed.

Figure 2 is a diagrammatic viewof operating parts. 1

Figure 3 is a diagrammatic view'of tion of the'constru'ction shown in Figure. 2.

Figure 4 is a diagrammatic view of another 45" modification of the construction shown in Figure2.

Figure 5 is a switch. 1 v I I "Figure 6 is a side eievatiomin detached position of cams employed. j

' Figure 7 is a' perspective view of meansfor causing a contact carryingmemb-er to act asa pacer:

Similar numerals indicate corresponding. parts. Referring to the clrawings z on the specimen under a modificaa discharge or feed line 3 to a control valve. 4 having a dial to indicate the pressure; A line 5 leads from the control valve't to the'press'ure cylinder 6 .of the testing machine. The lines 3 and 5 are thus pressure lines for the pressure cylinder 6. The pump 2 has a line I provided with a check valve 8 and leading tothe return cylinder 9 of the testing machine. A line Ill having a safety valve H leads to a return reservoir l2. The safety valve H is set for a pre determined pressure so that a predeterminedpressure will be maintained in the return cylinder 9 so that the piston of the pressure cylinder will be returned in the well" known manner during the operation of the-testing machine.

' Excess fluid from the duplex pump 2 is returned ftOllhe return reservoir I2 'by'pipes-"l3 and i4.

5 has'a' manually actuated, slow unloading valve 22. The overflow from the control valve-passes by line 23 to return line vi8'and therefrom to the reservoir l2. f I

The'valve i6 is controlled byan electromagnet 25; The movable part ofthe electromagnet is oper'atively connectedto thefvalve IE to actuate it. A rack 21 actuatedbythe crosshead motion,

turns a dial hand of the dial indicator of the weighing system of the testing machine in the on a shaft 29 suitablyjournalled' in a bearing bracket 3il.' The shaft 29 has acontact member 3! fixed to it so that it turns with the shaft. 'The i r I Eris rotatably adjustable onrthe shaft and can longitudinal section of atiming] switch 16 is not desired, to move its contacts 34 and 35 out ofvthepath of the arms 32 and'33,

- as shown in dotted lines'in Figure 5.

I 24 and its movable part istensioned by a spring conventional manner and also drives a pinion 28 x The current passes from a sourcev of volt supply by line 31 to a six volttransiormer-38 and therefrom by line39-to contact 34;,contact member 3|, contact-35 and line-Ml to solenoid turn from the electromagnet 24 is by line 45, cir-- cuit breaker 46 and line 41.

The solenoid switch 4| has a return line 48 to the transformer38 and the transformer 38 has a return line 49 to return line 41.

In some tests it is desirable to have the valve l6 intermittently opened at predetermined intervals so that hydraulic fluid will be intermittently by-passed in small quantities from feed line 3 to feed line 5. For this purpose a line 50 leads from line 31 to a switch 5|,

the latter having a line 52 leading to a motor 53.v

The return from the motor 53 is by line 54, switch 5|, line 55 and line 41.

The circuit breaker 46 serves only as a timer for the energization or de-energization of the electromagnet 24.

The shaft of the motor 53 has rotatably adjustableon it two cams 56 and 51, each of which has a cam face 58 and a dwell 59. By relative rotary adjustment of these two cams the times at which the circuit breaker is opened and closed may be varied.

60 designates the weighing system of the hydraulic testing machine which is controlled by the cross head motion of the testing machine to actuate the rack and thereby the dial hand 6| of the pressure indicator.

. In Figure 7, I have shown a contact member 65 corresponding to the stationary contact member 36 in Figure 2 but in the form of a gear inter geared with the shaft of a driving motor 66. In this case the contact member 65 is rotated to provide an interval of time before the arms 32 and 33 can close and open the circuit of the electro-' magnet through contacts 34 and 35.

The use of the motor 53 and its cams is optional.

In the embodiment shown in Figure 2, I provide means to automatically increase the pressure in {feed line 5.

In the embodiment seen in Figure 3 the control valve 4 is set for an overload and the pressure in feed line 5 is reduced to maintain a constant loading pressure in the pressure cylinder 6. In this case the construction is the same as that seen in Figure 2 except that the by-pass line I5 is omitted and the return line I8 is connected with the valve l6 so that when such valve i6 is open oil can pass from feed line 5, line H, valve I6 and return line l8 to the reservoir |2.

In the embodiment seen in Figure 4, instead of increasing the pressure in feed line 5 as in Figure 2, or reducing the pressure in feed line 5 as in Figure 3, the pressure is reduced in feed line 3. In this case, the line H of Figure 2 is omitted and the discharge from valve I6 is by line 64 to the reservoir I2. This reduces the pressure passing to the control valve 4. The operation will now be apparent to those skilled in this art and is as fallows:

When the pressure in feed line 5 is applied to the conventional ram or piston in the pressure cylinder 6, a loading pressure is created on the specimen under test which causes a variation in length of the test specimen. This actuates the by the setting of the safety valve l weighing system and causes the rack 21 to move.

The return cylinder 9 maintains a substantially constant pressure beneath the piston of the pressure cylinder 6 and when the loading pressure is released efiects the return of the piston of the pressure cylinder to its initial position for a new testing operation. The pressure in line I between return cylinder 9, check valve 8, and safety valve l I and in the return cylinder is determined The discharge from thesafety valve is by line H] to reservoir l2.

Assuming now that the specimen to be tested has been secured in place and referring to Figure 2, the control valve 4 is opened to a desired dial setting and the hydraulic fluid passes by feed line 3, control valve 4 and feed line 5 to the pressure cylinder 6. As the specimen changes in length due to the applied load, the rack 21 moves forwardly to turn the gear 26 and thereby the shaft 29 and contact member 3|. When the arms 32 and 33 engage the contacts 34 and 35 on the stationary contact member 36, the circuit is closed by the solenoid switch 4| and current passes by line 31, transformer 38, line 39, contact 34, contact arms 32 and 33, line 40', solenoid switch 4|, line 44 to electromagnet 24 to energize it and cause the valve l6 to open. Hydraulic fluid can now be by-passed around the control valve by line l5, valve l6 and line I! to feed line 5 to increase the pressure in feed line 5 to compensate for leakage of fluid by the piston in pressure cylinder 6.

If the arms 32 and 33 are moved-out of engagement with the contacts 34 and 35, the solenoid switch is de-energized thusopening the circuit, de-energizing the electromagnet 24 and the valve |6 closes'so that the only hydraulic fluid passing to the pressure cylinder 6 is by feed line 3, control valve 4 and feed line 5. If the loading pressure in the pressure cylinder 6 decreases below the predetermined loading pressure, the above cycle of operation is repeated.

The use of the circuit breaker 46 is optional. The cams 56 and 51 driven by the motor 53 are relatively adjustable so that their outer peripheries may form .acomplete circle in which case the circuit breaker is not operated. These cams may be relatively adjusted to form cam faces spaced a desired number of degrees apart so that the circuit breaker 46 will automatically open and close the electric circuit for the electromagnet 24 of the valve |6 at selected time intervals.

The operation of the embodiments seen in Figures 3 and 4 have been set forth in the detailed description. I

If the embodiment seen in Figure 7 is used, the time intervals for opening and closing the electric circuit can be varied since the gear 65 must rotate to bring the contacts 34 and 35 into the path of the arms 32 and 33 with which they cooperate.

If a quick unloading of the pressure in the high pressure cylinder is. desired, the quick unloading valve 20 is openedand fluid can pass from feed line 5 to line l8 and reservoir l2.

If a slow unloading of the pressure in pressure cylinder 6 is desired, the slow unloading valve 22 is opened and fluid from feed line 5 can pass by lines 2| and I8 to the reservoir .|2.

The pump 2 can be driven to provide an excess pressure in the line 3, or the required pressure for the pressure cylinder 6.

The return cylinder is shown to illustrate one manner of returning the piston in the high pressure cylinder, but it is to be understood that this is only for the purposeof illustration and any desired means may be employed for this purpose, such as forexample, springs, fluid pressure or the high pressure cylinder may be arranged so that its piston will return by gravity.

Having thus described my invention, what I claim as new and desire to secure by Letters Patentis:

1. In an automatic load'holder for hydraulic testing machines, having a high pressure cylinder, means to load the high pressure cylinder, an electromagnetic valve controlling the augmenting of pressure in the high pressure vcylinder,'and an electric circuit which includesth-e electromagnetic valve and has a circuit opening and closing device automatically controlled by the weighing system of the testing machine.

2. In an automatic load holder for hydraulic testing machines, having a high pressure cylinder, means to load the high pressure cylinder, an electromagnetic valve controlling the vaugmenting of pressure in the high pressure cylinder,

an electric circuit which includes the electromagnetic valve and has a circuit opening and closing device automatically controlled by the inder, an electric circuit which includes the electromagnetic valve-and has a circuit opening and closing device automatically controlled by the weighing system of the testing machine and a motor driven circuit breaker for said circuit and having adjustable means to vary the time the circuit is opened and closed by said circuit breaker. I I

4. In an automatic load holder for hydraulic testing machines, having a high pressure cylinder, means to load the high pressure cylinder, an

electromagnetic valve controlling the augmenting of pressure in the high pressure cylinder, and an electric circuit which includes the electromagnetic valve and has a circuit opening and H closing device including a stationary contact member and a movable contact member which latter is driven and automatically controlled by the weighing system of the testing machine.

5. In an automatic load holder for hydraulic testing machines, having a high pressure cylinder, means to load the high pressure cylinder, an electromagnetic valve controlling the augmenting of pressure in the high pressure cylinder, and an electric circuit which includes the electromagnetic valve and has a circuit opening and closing device and comprising a motor driven contact member and a cooperating contact member driven and automatically controlled by the weighing system of the testing machine.

6. In an automatic load holder for hydraulic testing machines, having a high pressure cylinder, means to load the high pressure cylinder, an

electromagnetic valve controlling the reducing.

of pressure in the high pressure cylinder, and an electric circuit which includes the electromagneticvalve and has a circuit opening and closing device automatically controlled by the weighing system of the testing machine.

7. In an automatic load holder for hydraulic 8. In an automatic load holder for hydraulic testing machines, having a high pressure cylinder, a motor driven pump supplying pressure to said return cylinder, a valve controlling the flow from said pump to the high pressure cylin-' ders, a by-passfrom the pump around the'control valve and leading to the high pressure cylinder, a valve for said by-pass, an electromagnet controlling the by-pass valve, and means automatically controlled by the weighing system to control said electromagnet and thereby maintain a uniform rate of loading for the high pressure cylinder, said automatic means including a motor driven circuit breaker.

9. In an automatic load holder for hydraulic I testing machines, having a high pressure cylinder, a motor driven pump supplying pressure to said cylinder, a valve controlling the flow from said pump to the high pressure cylinders, a bypass from the pump. around the control valve and leading to the high pressure cylinder, a valve for said by-pass, an electromagnet controlling the bypass valve, and means automatically controlled by the weighing system to control said electromagnet and thereby maintain a uniform rate of loading for the high pressure cylinder, said automatic means including a motor driven circuit breaker having adjustable means to time the opening and closing of the circuit of the electromagnet. v

'10. In an automatic load holder for hydraulic testing machines, having a high pressure cylinder, a motor driven pump, a supply line from the pump to the cylinder, a control valve for the supply line, a reservoir, a return line from the outlet side of the control valve to the reservoir, an electromagnetic valve controlling said return line, and an electric circuit which includes the electromagnetic valve and has a circuit opening and. closing device forming a part of the electric circuit'and controlled by the weighing system of the testing machine,

11. An automatic load holder ,for hydraulic testing machines, having a high pressure cylinder, comprising means to load the high pressure cylinder to maintain a substantially constant load indication, and means independent of the loading means: and controlled by the weighing system to augment the pressure in the high pressure cylinder to automatically maintain a substantially uniform rate of loading.

12. An automatic load holder for hydraulic tially uniform rate of loading.

ROBERT B. 

